linux/arch
Christian Borntraeger 3491caf275 KVM: halt_polling: provide a way to qualify wakeups during poll
Some wakeups should not be considered a sucessful poll. For example on
s390 I/O interrupts are usually floating, which means that _ALL_ CPUs
would be considered runnable - letting all vCPUs poll all the time for
transactional like workload, even if one vCPU would be enough.
This can result in huge CPU usage for large guests.
This patch lets architectures provide a way to qualify wakeups if they
should be considered a good/bad wakeups in regard to polls.

For s390 the implementation will fence of halt polling for anything but
known good, single vCPU events. The s390 implementation for floating
interrupts does a wakeup for one vCPU, but the interrupt will be delivered
by whatever CPU checks first for a pending interrupt. We prefer the
woken up CPU by marking the poll of this CPU as "good" poll.
This code will also mark several other wakeup reasons like IPI or
expired timers as "good". This will of course also mark some events as
not sucessful. As  KVM on z runs always as a 2nd level hypervisor,
we prefer to not poll, unless we are really sure, though.

This patch successfully limits the CPU usage for cases like uperf 1byte
transactional ping pong workload or wakeup heavy workload like OLTP
while still providing a proper speedup.

This also introduced a new vcpu stat "halt_poll_no_tuning" that marks
wakeups that are considered not good for polling.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Radim Krčmář <rkrcmar@redhat.com> (for an earlier version)
Cc: David Matlack <dmatlack@google.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
[Rename config symbol. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-05-13 17:29:23 +02:00
..
alpha alpha/extable: use generic search and sort routines 2016-03-22 15:36:02 -07:00
arc ARC fixes for 4.6-rc4 2016-04-11 12:19:57 -07:00
arm KVM: halt_polling: provide a way to qualify wakeups during poll 2016-05-13 17:29:23 +02:00
arm64 KVM: halt_polling: provide a way to qualify wakeups during poll 2016-05-13 17:29:23 +02:00
avr32 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2016-03-19 10:05:34 -07:00
blackfin arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
c6x arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
cris Merge branch 'mm-pkeys-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-03-20 19:08:56 -07:00
frv asm-generic changes for 4.6 2016-03-24 23:13:48 -07:00
h8300 h8300: switch EARLYCON 2016-03-25 01:45:19 +09:00
hexagon Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2016-03-19 10:05:34 -07:00
ia64 [IA64] Enable preadv2 and pwritev2 syscalls for ia64 2016-03-25 14:37:32 -07:00
m32r Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2016-03-19 10:05:34 -07:00
m68k m68k/defconfig: Update defconfigs for v4.6-rc2 2016-04-07 11:45:31 +02:00
metag arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
microblaze arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
mips KVM: halt_polling: provide a way to qualify wakeups during poll 2016-05-13 17:29:23 +02:00
mn10300 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2016-03-19 10:05:34 -07:00
nios2 nios2: Replace fdt_translate_address with of_flat_dt_translate_address 2016-03-31 08:15:45 +08:00
openrisc arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
parisc parisc: Update comment regarding relative extable support 2016-04-08 22:14:26 +02:00
powerpc KVM: halt_polling: provide a way to qualify wakeups during poll 2016-05-13 17:29:23 +02:00
s390 KVM: halt_polling: provide a way to qualify wakeups during poll 2016-05-13 17:29:23 +02:00
score Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2016-03-19 10:05:34 -07:00
sh arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
sparc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc 2016-03-28 15:14:11 -05:00
tile Merge git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile 2016-03-28 15:04:55 -05:00
um fs/coredump: prevent fsuid=0 dumps into user-controlled directories 2016-03-22 15:36:02 -07:00
unicore32 Merge branch 'mm-pkeys-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-03-20 19:08:56 -07:00
x86 KVM: halt_polling: provide a way to qualify wakeups during poll 2016-05-13 17:29:23 +02:00
xtensa Xtensa improvements for 4.6: 2016-03-20 12:22:07 -07:00
.gitignore
Kconfig objtool: Add CONFIG_STACK_VALIDATION option 2016-02-29 08:35:13 +01:00